1. Field of the Invention
The present invention relates to a head mounted video display for providing a monocular or binocular wide field of view image. More particularly, the head mounted display contains unique features that allow it to be light-weight, portable and capable of being worn like a pair of spectacles or goggles. The head mounted video display provides a magnified video image that is useful in many fields including aiding the vision of persons with impaired eye-sight.
2. Description of the Prior Art
Despite dramatic surgical and medical advances, most diseases of the eye and the visual system result in permanent visual impairments. More than 11 million people in the U.S. suffer irreversible visual impairments that cannot be corrected medically, surgically, or with eyeglasses. Out of this large group, approximately 2.5 million people have visual impairments so severe that the individual suffers a disability, this condition is called low vision. More than 2% of our population over age 40 have low vision; that is, visual acuity in the better eye is 20/70 or worse (for a much smaller percentage of people, low vision results from limited visual fields, i.e., "tunnel vision"). The percent of people with low vision increases with increasing age, an ominous statistic for the future, given our aging population.
Low vision severely limits or precludes reading, face and object recognition, driving, personal grooming, performance of visually-guided tasks (e.g., assembly work, inspection, design maintenance, etc.), and safe mobility (e.g., street crossing, climbing stairs, etc.). In many cases the limitations on visual functioning, reading in particular, can be lessened with the use of magnifying devices. That is, the limitations on visual performance imposed by low visual acuity often can be overcome by magnifying the image to a scale that is appropriate for the visual acuity. Typically this is accomplished with various types of optical magnifiers, however, in some situations closed-circuit television systems are used to obtain magnification. However, existing closed-circuit television magnification systems use existing television displays which are not portable and which require the low vision patient to scan across a greatly enlarged image on the television screen. A head mounted binocular display, mounted on the head like a pair of spectacles or goggles and providing separate video images to the two eyes for wide field binocular viewing would benefit low vision patients greatly, but is not taught by the prior art.
Similarly, binocular wide-field stereoscopic viewing that provides magnified video images would have application in various fields, including 3-D computer aided design. But, the prior art does not teach a binocular display, mounted on the head like a pair of spectacles or goggles. Head mounted displays in the prior art were developed for military applications and are extremely heavy and either require support by a head frame or are mounted on a helmet.
U.S. Pat. Nos. 3,582,191 and 4,672,436 describe head worn video displays. In each patent the video display is located in front of the subject's head rendering the technology inappropriate for a goggle-like or spectacle-like device. U.S. Pat. No. 4,806,011 discloses a pair of glasses incorporating a microfilm cassette that is used to project an image into the wearers eye. The reference however, does not teach generating a magnified video image.
The following articles discuss head mounted video displays designed for military applications and incorporated into helmet-like structures;
1. "Developing a wide-field of view HMD for Simulator" by Bill McLean and Steve Smith (SPIE vol.778 Display System Optics (1987)); PA0 2. "An integrated approach to Helmet Display System Design" by James E. Melzer and Eric C. Larkin (SPIE vol.778 Display System Optics (1987) PA0 3. "Low Cast Design alteration for Head Mounted Stereoscopic Display" by Stephen W. Martin (SPIE vol.1083 Three-Dimensional Visualization and Display Technology (1989).
The devices disclosed in these articles do not teach how to overcome the technical difficulties of incorporating the video display, the folded optics and the object mirror in a goggle-like display. Similarly an article entitled "Optical Design Criteria for Binocular Helmet/Mounted Display" by Martin Shenker (SPIE vol.789 Display System Optics (1987) teaches the use of a curved object mirror and a flat beam splitter to present an image to the subject's eye; but, does not disclose the folding optics necessary to incorporate both features onto a goggle-like head mounted display.
An article entitled "Exploring Virtual Worlds with Head Mounted Displays" by J. C. Chung et. al (SPIE vol.1083 Three Dimensional Visualization and Display (1989)) explores the usefulness of head mounted displays in various fields; but the article does not teach how to design a goggle-like head mounted display. Similarly, an article entitled "The Programmable Remapper Clinical Application for Patients with Field Defects" by David S. Loschin and Richard D. Juday (Optometry and Visual Science, vol.66 #6, pages 389-395) teaches the advantages to low vision patients that could be provided by a goggle-like head mounted display, but does not suggest a practical design for such a goggle-like head mounted display.